QF loads across the Pacific are also heavy at present due to seasonal influences - mid year school holidays in Oz & the big summer holidays coming up in the US. I've no idea on the yield though and that is the critical thing for an airlines financial well being.
My read on the announcement of reduction in QF services is just formalising what is already happening with flights being cancelled when loads are light, ie there has been 1-2 AKL-LAX cancellations per week as well as occasional BNE-LAX and QF11/12 SYD-LAX flights. Flights are adjusted in an attempt to maximise yield (ie minimise losses) whilst minimising disruptions to pax - it's a fine balancing act. From what I've been hearing, V Oz is doing the same thing, adjusting flights to suit the loads.
Delta's start on 1st July will look good for the first month due to US summer holiday demand and the B777-200LR looks to be a good sized aircraft to develop a new international route, but in the long term, the competition will be cut-throat. I suspect that there won't be profits made on the route for a couple of years & it's quite probable that United will withdraw from its Oz routes to stop the heamoraging of cash.